1. Field
This invention pertains in general to nuclear power plants and, more particularly, to systems and methods for evaluating the tubes of a steam generator of a nuclear power plant. In particular, the software tools and methods of the invention integrate two automated analysis processes and the results generated therefrom.
2. Description of Related Art
Nuclear power plants can be generally described as including a reactor that has one or more fuel cells, a primary loop that cools the reactor, and a secondary loop that drives a steam turbine to operate an electrical generator. Typically, such nuclear power plants additionally include a heat exchanger positioned between the primary and secondary loops. The heat exchanger is in the form of a steam generator which includes tubes that carry the primary coolant and a plenum that carries the secondary coolant in heat-exchange relationship with the tubes and therefore, with the primary coolant.
It is known in the industry that the tubes of a steam generator are subject to wear from mechanical vibration, corrosion, and other mechanisms. Both manual and automated processes have been developed to detect and address this concern. Period inspection of the tubes of a steam generator for wear is necessary to avoid failure of a tube and the consequences resulting therefrom, for example, potential nuclear contamination of the secondary loop.
Known manual and automated processes have limitations associated therewith. For example, methods of measuring tube-to-tube proximity (i.e., the spatial relationship between two adjacent steam generator tubes), a potential precursor for tube-to-tube contact wear, has been found to be cumbersome and unreliable. Guidelines, analysis training and process changes have been implemented in the art with varying levels of success.
A known method of inspecting the tubes of a steam generator involves the insertion of an eddy current sensor into one or more of the tubes. A signal is received from the eddy current sensor, which is in the form of a voltage and a phase angle. An analyst can review the signal data to ascertain the current condition of the tubes of the steam generator. However, the analyst must possess a high degree of expertise in order to accurately ascertain from the signal data the current condition of the tubes of the steam generator. A typical steam generator may possess between three thousand and twelve thousand tubes, by way of example, with each tube being several hundred inches in length. Thus, the review of eddy current data can require a large expenditure of time by the analyst.
Among the difficulties involved in the analysis of eddy current data is the determination of whether a signal is indicative of a possible failure of a portion of a tube or whether the signal is not indicative of such a failure. Each tube of a steam generator typically has a number of bends and mechanical supports. In passing an eddy current sensor through such a tube, the signal from the eddy current sensor will vary with each mechanical support and bend, and the signal also will vary in the presence of a flaw, such as a crack or a dent in the tube. As such, the difficulty in analysis involves the ability to determine whether a change in a signal from an eddy current is indicative of a known geometric aspect of a tube, such as a bend or support, in which case further analysis of the signal typically is unnecessary, or whether the change in signal from the eddy current sensor is indicative of a crack or a dent, in which case further analysis of the signal typically is necessary.
Current steam generator inspection processes, in accordance with industry guidelines, requires the operation of two separate and independent analysis processes. These processes, described as primary analysis and secondary analysis, are operated either manually or through an automated system. EPRI, an industry institute that issues guidelines, has established that, if both processes are being used, such processes have to be different, independent and qualified by EPRI. The output of each of the primary analysis and secondary analysis processes produces separate primary analysis and secondary analysis reports. These reports need to be resolved by a resolution process to produce a single final result, which eventually determines the overall conditions of the steam generator tubes.
Enhanced Automated Data Screening (EADS) and Real Time Automated Analysis (RTAA) are two automated analysis processes known in the art for use in inspecting steam generator tubes for degradation. EADS is a rule based vector extraction algorithm and RTAA is a noise based signal extraction algorithm. These algorithms complement each other and provide effective primary analysis and secondary analysis in compliance with current industry guidelines.
Both EADS and RTAA have proven records to be effective analysis methods for all type of steam generator inspection tubing. However, there are disadvantages associated with these known steam generator tube analysis processes. For example, significant time and effort may be necessary to analyzing the two separate reports and data generated by the EADS and RTAA analyses.
It is, therefore, an object of this invention to provide an automated analysis of steam generator tube conditions as an alternative to the existing inspection process. It is desired that two separate and independent automated analysis processes, e.g., a primary analysis and a secondary analysis, be combined and integrated into a single efficient automated analysis system. In addition, several supporting software modules may be integrated and run on a standard computer to produce final results accurately and promptly. The invention provides a combined analysis report from the two analysis processes to produce the final results of steam generator tubing inspection in a single report for review, enabling users to identify the automated analysis processes that generate the tube condition report entries, and integrating a noise evaluation process. This new automated analysis can demonstrate increased performance and reliability with respect to the evaluation of steam generator tubing data. It is anticipated that the results and the single report of the results will provide comprehensive steam generator repair solutions that will preclude failures and unplanned shutdowns that are time-consuming and costly.